Research On Mechanical Parts Of Condition Monitoring System Based On Danger Theory

As the science and technology developing, the mechanical system is more and more complex,however, it’s security couldn’t keep up with the pace of the development apparently. Now accidentscaused by mechanical failure are more and more, as much as60%of them are fatigue failure ofmechanical parts. Although the working condition and environment of mechanical parts has beenconsidered in the design phase, however the working condition is very complex caused by wrongoperation of employees or other reason in the actual work. Some of the standard deviation in designphase is inevitable in the actual situation, so it’s necessary to real-timely monitoring and evaluatethe state fatigue life of mechanical parts.In general, we need to replace the parts when the real life meets the limit design service life,perhaps we should regular inspection and maintenance it in the using time. But it will causeaccidents if we continue according to the design condition for replacement or repair due to thedeviation between the actual condition and design condition in the limits of life. In view of thedeviation between the design limit life and the actual limit service life, both the reliability andfatigue life to determine the using condition of fatigue in danger theory is proposed to achieve thepurpose of more accurate fault forecast.First, this paper designed the signal acquisition and signal processing system. The signalacquisition device used the low cost, good linear, high sensitivity resistance strain gauge. Softwarethis paper used the comprehensive functions mechanical system testing and fault diagnosis softwarefor data preprocessing (remove the “sharp” and “burr” on data), and then used the rain flow plate ofthe software for counting and statistics.Secondly, correct the life using condition method is proposed in view of the deviation betweenthe design limit life and actual limit life. Through the initial damage and the load damage in thesampling period, the sum residual fatigue life is assessed. The condition of limit using life isredefined by using the ratio of the sum of the service life and the residual life in design life. At theend of this article the feasibility of the condition was verified by software simulation.Third, the reliability of mechanical components is calculated according to the cumulativedamage model and the fatigue life model. The fatigue life state monitoring system based on thedanger theory was put forward, this theory defined the danger signal by combining the limit usingfatigue life condition and the limit using reliability, and then divided the risk range. According tothe different risk range, the system made different response and gave the solution. At the end of thisarticle the rationality of the algorithm is verified by experiment.Fourth, the fatigue life condition monitoring system was applied in the electric car wheel hub bearing unit fixed bolts, it verifies the validity of the algorithm. This paper designed the intelligentwheel hub bearing fixed bolts fatigue life condition monitoring bench.